Performance of Viscoelastic Dampers in World Trade Center Towers

The viscoelastic damper was conceived and developed as a part of the structural design for the Twin Towers of the World Trade Center, New York. They are an integral and an essential part of the structural system, being designed to assist the tubular steel frame in limiting wind-induced building oscillation to levels below human perception. The selection, quality, shape and location of the dampers was based on the dynamic analysis of the towers (computer modeling, wind tunnel, etc. ), and of the damping acquired to achieve performance standards. This paper presents information from the dynamic monitoring program, reports on the methods used to evaluate the effectiveness of the dampers, and compares overall structure damping with that calculated during structural design.